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In this lesson, we're going to walk

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through how the troubleshoot processes

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within the Linux system.

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Now, during your operation

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on the system might encounter various issues

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that degrade the performance,

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and it makes the system unusable.

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So common cases are process hangups causing instability

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that a process consuming too many resources,

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making the system sluggish in general.

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So we're going to go through

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and learn how to identify these processes,

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Figure out the current states that they should be in,

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like running interruptible sleep,

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uninterruptible sleep, zombie mode,

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different ways to kill processes and view them.

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So let's get started.

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Now, the first command we're going to go over,

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is the process command.

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Now by default, what it does is,

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it identifies the current processes,

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that's running in this shell by the user, okay?

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So right now, we always know Bash is the default shell

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for this Linux distribution.

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So that's always going to be running in the background for us.

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And that process command is what we just executed.

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Now, if you see, that has a process ID,

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and this is going to be vital when it comes

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to identifying services, killing processes,

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changing priorities, things of that nature.

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Now, in order to see everyone's process,

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we can use the dash e option,

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and that's going to show us all the processes

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that are currently running on the system.

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Okay, we see there's a lot of them running,

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and again, practice with the less command.

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We want to see it from top to bottom.

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Remember, there's our systemd there, always the first one.

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And each process always increments one after the other,

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of course, starting with the first in it,

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which going to be systemd for us.

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Sometimes there'd be a situation

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where you don't actually know the process ID.

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To quickly do it use the P grep command.

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And so, for example, we're going to use sshd.

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That's going to be the secure shell daemon, quick command,

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enter the process that we're looking for,

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and it's going to spit out the process ID.

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Now there'll be times where you're running process

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typically as script,

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and you need to run that process in the background,

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meaning that it's not going to consume,

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the entire commands line screen, okay?

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So we're going to use the ampersand symbol

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at the end of the command,

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and that's going to allow it to go into the background.

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And now we're going to use the sleep command,

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just to see this happen, right?

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So we're going to do sleep,

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300 seconds ampersand,

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okay?

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So it spits out the process ID for us,

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and we're going to run this process just

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to see that it is actually running.

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Okay, now, as mentioned earlier,

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we're going to learn how to kill processes,

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and we'll use the kill here,

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just to end this command.

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Okay?

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Going to run this again.

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And we see that that process was terminated, okay?

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Another useful command that we can use is the top command.

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And what this does is, it's like an interactive prompt

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to allow us to see all the process's memory consumption,

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and CPU consumption.

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It's usually going to be the most important and vital.

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And here, we're also able to change the nice values,

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which coordinate with the priority of the process.

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So, we're going to check this out.

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We're going to use the uppercase M,

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and that allows us to sort everything

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by the amount of memory that is taken up.

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So you see the top one is the shell that we're running.

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That's consuming the most memory currently.

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And then we also can do capital P,

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and that's going to sort things by the CPU process,

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whatever's running the highest CPU process.

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Currently, not a lot of things are running.

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A lot of things are very,

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using very minimal CPU process.

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But in a enterprise environment,

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there will be a lot of processes running,

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and some will consume the CPU and memory heavily.

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List of lsof, it shows us a list

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of the files that are currently being ran,

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and the processes that are running them, okay?

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So again, let's try to see this

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from the top and we can see the command process ID, user,

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we get the name of the file that's being open, et cetera,

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a lot of get useful information about this one.

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Again, remember, this is all relative

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to the files that we're trying to open

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because it can be situations where you're unable

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to open a certain file that you're trying to,

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and it's because of processes hogging

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up the particular object.

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As we saw earlier, that systemd,

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that's the initial boot process.

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Now, we're going to use this again for the analysis.

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We're going to analyze the boot order, okay,

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and we see this command.

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It's mostly going to be used with the blame command,

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and that's to see how long it actually takes

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for all the processes to run it.

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So it, by itself, just gives us how long the startup takes,

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and that's for us to identify any performance issues.

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But when we do it this way, we add the blame,

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it gives us all the services

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to go see how long it took them to start, okay?

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This will definitely be useful,

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when we're troubleshooting any type of booting up process.

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All right, next, we're going to go through,

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and learn how to modify the priority of systems.

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Now, typically, the scheduler is pretty effective

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at scheduling and prioritizing processes

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that need to be ran in a certain order.

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But again, it'll be time where we want

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to increase the priority,

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and let the system know, Hey, we want this done first.

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And so we want to use this command really quick, xl,

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and it's going to give us the priorities run by the user,

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and it shows the nice values of them.

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By default, the nice value is going to be zero,

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and the lower the priority,

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the lower the number, the higher the priority.

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And it's going to range from negative 19 to 20.

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So, anything with negative 19,

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it's going to be first, and 20 will be last,

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and anywhere in between.

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Okay, so we're going to simulate a long-running process,

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switch bit,

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and this command is just going to be an iteration of copies.

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Okay, so, we see the process ID, 15, nine, four, seven,

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15, nine, four, seven.

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We want to use the sudo top command,

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'cause we want to change the nice value of this.

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Okay?

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So, we're going to go in here, and do R.

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And going to do 15,

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nine, four, seven.

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Okay.

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And we're going to change this value to negative 15.

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A little quick.

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I'm going to look here, see if it went through for us.

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Okay, so we see I had that folder,

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taken care of,

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and again,

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pretty much as soon as we got,

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as soon as we changed that nice value,

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you can see at the bottom, how it says, done.

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Now, with quick processes, our, our CPUs are there so fast,

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that they can get done with copy processes pretty quickly,

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but changing that priority really amped it up.

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And so that's going to just indicate that, hey,

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we were able to copy the Etsy folder

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into a backup directory very quickly.

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Okay, so we went over how to troubleshoot certain processes

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by identifying the process IDs, how to kill them,

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how to run processes in the background,

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and how to change the priority that the scheduler uses

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for processes when we're running commands

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on our Linux system.

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Thank you for sticking with me through this walkthrough,

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and I'll see you in the next lesson.